Method of effecting delayed hardening of films and resulting product



, 1T0 Drawing. V i

V retard the a-ctivating reagent, at least; tern porarily; andthereafter toso treat'thesarne' 25 asito remove 'or overcome the effectivenessof Patented Mar. 29, 1932 uNrrmsm-T JZQHN EJK NNINBER, or NOBTE GAMBRIIJ in-on,- on

mnmnon or n'rrncrrme DELAYED nennnnino or Finnsnn nnsumine rnonuc'r Application and April 1,

V This invention relates to a method of obtaining a delayed hardening? effect, socalled, in; colloidal substances such as gelaa tine (in the form of films and coatings as commonly employed in photography and related arts)" and to the resnltingproduct. I

It is anobject of the invention'to arrest or retard the action of hardening agents upon colloidal emulsions or solutions, (as of the restraining agent, either in whole or in part, and to permit or'cause; the hardening reaction to proceed accordingly.

The, hardening agent is characterized by its property to harden thecolloidal emulsion or solution'( typically gelatine) under suitable conditions, usually of areducing nature, and is exemplified generally by the soluble alkali; bichromates including ammonium bich-romate. Ordinarily potassium bichromate is used forthispurpose. The term harden Vl i'ngf as, herein employed isnot intended to mean-mechanical rigidity but to-signify the alteration of the gelatine whereby it is rendered more insoluble in water and the penetration and absorption of dye solution and through the outer portion of the gelatine layer is restricted}, but without inhibiting the a like; coloringagents into the surface or uniform wettingby a dye-solution-in areas printed therewith and Without overcoming the exibility, uniformity and strength 10f The activating reagent is characterized by manifestingfasuitable reducing actiOn-(usu V GE,messnonusnrrsgss enon To anon-KL cononnorion mornnn conronarron,

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on Bosmon, MASSACHUSETTS, A. soonnona- 1927; "seri iflno; 180,339;

ally under positively alkaline or acid con- I? ditions); to render the hardening agent effective With respect to its hardening reactionuponthe colloidal emulsion or solution. representative group of such reagents is found} in the alkali sulfites (or bisulfites) in eluding ammonium sulfiteor bisulfite.

Preferably, such activation of the harden ing re action is substantially prevented while theemulsion or solution isina liquid condition and efi'ectuated during or after appreciable solidification and/or dehydration of the To this end a restrain I ing agent "is employed which isprimarily I characterizedby rendering the activating" re with respect to the harden s" time hastaken place.

agentinefi'ective ing reaction and by beingremovable from the emulsion: or solution Y (preferably during or after solidificationof the same) without physical disruption or harmful decomposition of the remainingconstituents, thereby t'opermit or cause the hardening function in-ythe desiredfmannerg The invention illbe described as-applied toethehardening of gelatine-films, and more reagent to I especially of films intended for use as blanks for the reception offdye images thereon by nnbibition printing;

For this purpose agelatine emulsion or 'solution may ffirst be prepared in accordancewith usual practices of thevartandfan appropriate amount of sodiumor ammonium bichromate is dissolved therein; ating' reagent, which may be sulfurousaaoid, a'soluble bisul fite'or ammonium sulfite is also added insuitable proportions. For example", 5% ofsodium bichromate and 5% of ammoniumfsulfite (upon the weight of gelatine) aire-suitable-amounts for-most purposes. The restraining agent is added in sufiicient quan my to as i The act'i-,

sure its restraining action beingef fectiye, due regardbeing taken of the nature I of the ot e re Present" I Thus, with 5% ammonium: sulfite HS: 'the actiyating agent 5% of concentrated ammonium; hy-

droXidev solution is -ordinarily suflicient. If I ammonium :bisulfite is employed, however,

more of the ammoniumrhydroxidel will be re:-

quired; o a

s As thusaprepared,thehardeningreaction of the usual backing materials,

solidification of the gelatine mass,

dominates, and upon the gelatine solution or emulsion does not proceed at all or goes on only at an extremely slow rate, so that the hardening eflect is not appreciable over long periods of time. The emulsion or solution may now be applied to such as celluloid strips, in the customary manner. Upon heating and drying the film, and the consequent stiffening or solidification of the gelatine coating, the restraining agent is gradually expelled and the activating reagent and hard ening agent are permitted to become effective to react and harden the solidifying gelatine mass, or to accelerate the hardening reaction of the gelatine. Extensive dehydration or however,

appears to slow up or prevent the progress of the hardening reaction. Accordingly,

when the moisture content of the mass has been reduced, for example, to or less,

so subsequent hardening action is again extremetions generally accelerate the hardening reaction while the continuance of the alkaline conditions induced by the excess of ammonium hydroxide prevents or greatly retards the hardening so long as its influence prephysical solidification (or drying) beyond the gel condition the further progress of the hardening reaction is inhibited.

It is to be understood that the commencement and cessation of the hardening reaction are not accompanied by any positive indications in the reactive mass, but that they may take place both in solutions or emulsions and in the dried film. However, under normal atmospheric conditions and relatively low temperatures, such reaction is extremely slow and hardly detectable or significant in its results, so far as the usual applications of the final products are concerned. But at room temperature F.) hardening will ordinarily proceed quite rapidly. Likewise, the finished hardened product is relatively permanent with respect to its desired characteristic properties if proper proportions of original materials have been used.

It will be readily appreciated by those skilled in the arts to which it appertains that numerous applications of the invention may $5 be made and that various substitutions and modifications may be resorted to for s cific purposes and for the obtainment of di erent hardening efiects, but it is considered that such substitutions and modifications are comprehended by eluded by the following claims.

I claim:

1. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble bichromate hardening agent, sulphurous acid and ammonia, and drying.

2. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble bichromate hardening agent, sulphurous acid and ammonia, drying and subsequently controllably removing the ammonia concomitantly with the solidification and hardening of the gelatine.

A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble alkali metal bichromate hardening agent, a reducing sulphite and ammonia, and subsequently drying and controllably removing the ammonia with concomitant solidification and hardening of the gelatine.

4. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble alkali metal bichromate hardening agent, a reducing alkali metal sulphite and ammonia, and subsequently drying and controllably removing the ammonia with concomitant solidification and hardening of the gelatine.

5. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble alkali metal bichromate hardening agent, a reducing alkali metal bisulphite and ammonia, and subsequently drying and controllably removing the ammonia with concomitant solidification and hardening of the gelatine.

6. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble alkali metal bichromate hardening agent. a reducing ammonium sulphite and ammonia, and subsequently drying and controllably removing the ammonia with concomitant solidification and hardening of the gelatine.

7. A method of preparing hardened gelatine films which comprises incorporating with an aqueous emulsion or solution of gelatine a soluble alkali metal bichromate hardening agent, a reducing ammonium bisulphite and ammonia, and subsequently drying and controllably removing the ammonia with concomitant solidification and hardening of the gelatine.

the above disclosure and in- 8. A solidified gelatine emulsion containing abichromate hardening agent, a reducing sulphite and ammonia, the uantity of the ammonia being suflicient su stantially to counteract'the activator andremovable to permit hardening at an optional time after the emulsion is solidified.

9. A solidifiedgelatine" emulsion contain ing a'bichromate hardening agent, an alkali metal sulphite and ammonia, the quantity of the ammonia being suflicient substantially to counteract the activator andremovable to permit hardening at an optional time after the emulsion is solidified.

10. 'A solidified gelatine emulsion containing a bichromate hardening agent, an alkali metal bisulphate and ammonia,'the quantity of the ammonia beingsufficient substantially to counteract the activator and removable to V I permit hardeningat an optional timeafter the emulsion is solidified.

11. A solidified gelatine emulsion contains ing a bichromate hardening agent, ammonium sulph ite and ammonia, the quantity of the ammonia being suflicient substantially to counteract the activator and removable to permit hardening at an optional time after the emulsion is solidified.

12. A solidified gelatine emulsioncontaining a bichromate hardening agent, ammonium. bisulphite and ammonia, the quantity of the ammonia being sufficient substantially to counteract the activator and removable to permit hardening at an optional time after th emulsion is solidified.

Signed by me at Boston, Massachusetts, this tWenty-sixthday of March, 1927.

JOHN .F. KIENNINGER. 

